U.S. patent application number 17/275767 was filed with the patent office on 2021-10-21 for low-cost and self calibrating clamp-on ultrasonic transducer.
This patent application is currently assigned to The University of Warwick. The applicant listed for this patent is The University of Warwick. Invention is credited to Steven DIXON, Jonathan HARRINGTON, Zhichao LI.
Application Number | 20210325218 17/275767 |
Document ID | / |
Family ID | 1000005748391 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210325218 |
Kind Code |
A1 |
DIXON; Steven ; et
al. |
October 21, 2021 |
LOW-COST AND SELF CALIBRATING CLAMP-ON ULTRASONIC TRANSDUCER
Abstract
A clamp-on ultrasonic transducer is disclosed. The clamp-on
ultrasonic transducer comprises an ultrasound-propagating wedge
having a first face and a second face which is inclined to the
first face. The clamp-on ultrasonic transducer further comprises a
first piezoelectric element which is mounted on the second face and
which is directed obliquely at the first face. The wedge has a
width, w, between first and second side walls, wherein the width,
w, is less than or equal to 10 mm.
Inventors: |
DIXON; Steven; (Coventry,
GB) ; LI; Zhichao; (Coventry, GB) ;
HARRINGTON; Jonathan; (Coventry, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The University of Warwick |
Warwickshire |
|
GB |
|
|
Assignee: |
The University of Warwick
Warwickshire
GB
|
Family ID: |
1000005748391 |
Appl. No.: |
17/275767 |
Filed: |
September 6, 2019 |
PCT Filed: |
September 6, 2019 |
PCT NO: |
PCT/GB2019/052484 |
371 Date: |
March 12, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01F 1/662 20130101;
G01F 1/667 20130101; G01F 15/185 20130101 |
International
Class: |
G01F 1/66 20060101
G01F001/66; G01F 15/18 20060101 G01F015/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2018 |
GB |
1814909.6 |
Claims
1. A clamp-on ultrasonic transducer comprising: an
ultrasound-propagating wedge having: a first face; and a second
face which is inclined to the first face; and a first piezoelectric
element which is mounted on the second face and which is directed
obliquely at the first face; wherein the wedge has a width, w,
between first and second side walls, wherein the width, w, is less
than or equal to 10 mm.
2. The clamp-on ultrasonic transducer of claim 1, wherein the wedge
is injection moulded.
3. The clamp-on ultrasonic transducer of claim 1, wherein the wedge
consists of polyetheretherketone.
4. The clamp-on ultrasonic transducer of claim 1, wherein the
width, w is between 5 and 9 mm.
5. The clamp-on ultrasonic transducer of claim 1, wherein the first
face is flat.
6. The clamp-on ultrasonic transducer of claim 1, further
comprising: a third face which is parallel to the first face; and a
second piezoelectric element which is mounted on the third face and
which is directed perpendicularly at the first face.
7. A clamp-on ultrasonic transducer comprising: an
ultrasound-propagating wedge having: a first face; and a second
face which is inclined to the first face; and a first piezoelectric
element which is mounted on the second face and which is directed
obliquely at the first face; wherein the wedge consists of
polyetheretherketone and the wedge is injection moulded.
8. A clamp-on ultrasonic transducer comprising: an
ultrasound-propagating wedge having: a first face; a second face
which is inclined to the first face; and a third face which is
parallel to the first face; a first piezoelectric element which is
mounted on the second face and which is directed obliquely at the
first face; and a second piezoelectric element which is mounted on
the third face and which is directed perpendicularly at the first
face.
9. A pipe clamp for a clamp-on ultrasonic transducer, the pipe
clamp comprising: first and second parts closeable around a pipe;
at least one hinge on a first side of the pipe clamp; at least one
closure on a second side of the pipe clamp; and at least one slot
in the first or second part for receiving at least one sensor such
that when the first and second parts are closed around the pipe,
the sensor is presented to the pipe.
10. The pipe clamp of claim 9, wherein the first and second parts
are formed of plastic.
11. The pipe clamp of claim 9, wherein the pipe clamp comprises:
first and second hinges spaced apart along the first side of the
pipe clamp.
12. The pipe clamp of claim 9, wherein the pipe clamp comprises:
first and second closures spaced apart along on the second side of
the pipe clamp.
13. The pipe clamp of claim 9, wherein the first part includes at
least one integrally-formed first hinge part, and the second part
includes at least one integrally-formed second hinge part arranged
to cooperate with the at least one first hinge part so as to form
the at least one hinge.
14. The pipe clamp of claim 9, wherein the first part includes at
least one integrally-formed first closure part, and the second part
includes at least one integrally-formed second closure part
arranged to cooperate with the at least one first closure part so
as to form the at least one closure.
15. The pipe clamp of claim 9 which is a two-piece pipe clamp
consisting of the first and second parts.
16. A clamp-on ultrasonic transducer assembly comprising: the pipe
clamp of claim 9; and at least one sensor comprising at least one
clamp-on ultrasonic transducer received in the at least one slot,
the at least one clamp-on ultrasonic transducer comprising: an
ultrasound-propagating wedge having: a first face; and a second
face which is inclined to the first face; and a first piezoelectric
element which is mounted on the second face and which is directed
obliquely at the first face; wherein the wedge has a width, w,
between first and second side walls, wherein the width, w, is less
than or equal to 10 mm.
17. A method of using the ultrasonic transducer of claim 6
installed on a pipe through which a fluid flows, the method
comprising: using a first piezoelectric element for a flow
measurement; and using the second piezoelectric for obtaining a
value for ultrasound velocity in a fluid in the pipe.
18. The method of claim 17, further comprising: using the value of
ultrasound velocity to obtain a value of flow rate through the
pipe.
19. (canceled)
20. A computer program product comprising a computer readable
medium storing the computer program comprising instructions:
measuring flow using a first piezoelectric element and obtaining a
value for ultrasound velocity in a fluid in the pipe using the
second piezoelectric.
Description
FIELD
[0001] The present invention relates to a clamp-on ultrasonic
transducer.
[0002] The present invention also relates to a clamp-on ultrasonic
transducer assembly comprising a pipe clamp and at least one
clamp-on ultrasonic transducer for clamping onto a pipe and for
measuring flow rate of a fluid through the pipe.
[0003] The present invention also relates to a method of using a
clamp-on ultrasonic transducer for measuring flow rate of a fluid
through the pipe.
BACKGROUND
[0004] Ultrasonic, clamp-on, transit-time flow metering is
extensively used for measuring flow of liquids and, to a lesser
extent, gases in pipes. This type of metering involves clamping two
or more transducers (or "sensors") to the outside of a pipe in
which a liquid is flowing. One transducer generates an ultrasonic
wave that enters the pipe wall, and travels through the liquid. The
wave can then couple through the pipe wall and be detected by the
second transducer or bounce within the liquid column several times
before being detected by the second transducer, which can be
clamped on the same side or on the opposite side of the pipe as the
first sensor. The process is reversed so that the second transducer
generates an ultrasonic wave that travels along the same path (but
in the opposite direction) and is detected by the first transducer.
The difference in the transit time for these two wave packets is
related to the liquid flow rate through the pipe. The wave that
travels generally in a downstream direction (i.e., with the flow)
takes a shorter time to cover the same distance, than the other
wave which generally travels in an upstream direction.
[0005] A significant component cost is the cost of the transducers.
Typically, the transducers are made from polyetheretherketone
(PEEK) and may be enclosed in a stainless-steel housing for
protection. Although PEEK has superior mechanical properties for
ultrasonic wedges in that it has favourable elasticity and low
attenuation, it is expensive in both material and manufacturing
costs compared to most other plastics since the starting material
is expensive and requires extensive machining starting from a solid
bar or block.
[0006] Although injection moulding of PEEK is possible, if
components are made using PEEK, then they tend to be made using
PEEK containing a filler, such as glass fibre. Introducing other
materials into PEEK, especially if they introduce inhomogeneities,
tends to increase ultrasonic attenuation. Moreover, injection
moulding of PEEK tends to require specialist machines, operating at
higher pressures and temperatures than is normally required for
injection moulding materials, such as ABS. The moulds for injection
moulding PEEK also need specific design considerations.
SUMMARY
[0007] According to a first aspect of the present invention there
is provided a clamp-on ultrasonic transducer. The clamp-on
ultrasonic transducer comprises an ultrasound-propagating wedge
having a first face and a second face which is inclined to the
first face. The clamp-on ultrasonic transducer further comprises a
first piezoelectric element which is mounted on the second face and
which is directed obliquely at the first face. The wedge has a
width, w, between first and second side walls, wherein the width,
w, is less than or equal to 10 mm. This can help to reduce the cost
of manufacture, for example, by allowing the wedge to be made by
injection moulding when it might otherwise not be possible to form
from injection moulding and/or allow the transducer to be used with
pipes of a range of diameters.
[0008] The wedge may be injection moulded. The wedge may consist of
or essentially consist of polyetheretherketone (PEEK). If the wedge
consists of or essentially consists of PEEK, then the wedge is
preferably injection moulded and, more preferably, does not contain
any filler, such as glass fibre.
[0009] The width, w, is preferably between 5 and 9 mm.
[0010] The first face may be flat. Alternatively, the first face
may be concave for better fitting to a pipe.
[0011] The clamp-on ultrasonic transducer may comprise a third face
which is parallel to the first face, and a second piezoelectric
element mounted on the third face and which is directed
perpendicularly at the first face. Thus, the second piezoelectric
element can be used to send waves perpendicularly through the pipe
wall to obtain a value for ultrasound velocity in a fluid in the
pipe.
[0012] According to a second aspect of the present invention there
is provided a clamp-on ultrasonic transducer. The clamp-on
ultrasonic transducer comprises an ultrasound-propagating wedge
having a first face and a second face which is inclined to the
first face. The clamp-on ultrasonic transducer further comprises a
first piezoelectric element which is mounted on the second face and
which is directed obliquely at the first face. The wedge consists
of or essentially consists of PEEK and is injection moulded. This
can help to reduce the cost of manufacture. The wedge preferably
does not contain any filler, such as glass fibre.
[0013] According to a third aspect of the present invention there
is provided a clamp-on ultrasonic transducer comprising an
ultrasound-propagating wedge having a first face, a second face
which is inclined to the first face, and a third face which is
parallel to the first face. The clamp-on ultrasonic transducer
comprises a first piezoelectric element which is mounted on the
second face and which is directed obliquely at the first face, and
a second piezoelectric element which is mounted on the third face
and which is directed perpendicularly at the first face.
[0014] Thus, the second piezoelectric element can be used to send
waves perpendicularly through the pipe wall to obtain a value for
ultrasound velocity in a fluid in the pipe.
[0015] According to a fourth aspect of the present invention there
is provided a pipe clamp for a clamp-on ultrasonic transducer, the
pipe clamp comprising first and second parts closeable around a
pipe, at least one hinge on a first side of the pipe clamp, at
least one closure (for example, a clasp) on a second side
(preferably opposite side) of the pipe clamp and at least one slot
in the first or second part for receiving at least one sensor such
that when the first and second parts are closed around the pipe,
the sensor is presented to the pipe.
[0016] The first and second parts are preferably formed of
plastic.
[0017] The pipe clamp may comprise first and second hinges spaced
apart along the first side of the pipe clamp. The pipe clamp may
comprise first and second closures spaced apart along on the second
side of the pipe clamp.
[0018] The first part may include at least one integrally-formed
first hinge part, and the second part includes at least one
integrally-formed second hinge part arranged to cooperate with the
at least one first hinge part so as to form the at least one hinge.
The first part may include at least one integrally-formed first
closure part, and the second part includes at least one
integrally-formed second closure part arranged to cooperate with
the at least one first closure part so as to form the at least one
closure.
[0019] The pipe clamp is preferably a two-piece pipe clamp
consisting of or essentially consisting of the first and second
parts.
[0020] According to a fifth aspect of the present invention there
is provided a clamp-on ultrasonic transducer assembly comprising
the pipe clamp and at least one sensor comprising the clamp-on
ultrasonic transducer received in the at least one slot.
[0021] The clamp-on ultrasonic transducer assembly may comprise two
or more sensors, for example, three or four sensors. Each sensor
may be received in a respective slot. Two or more sensors may be
received in one slot.
[0022] According to a sixth aspect of the present invention is
provided a method of using the ultrasonic transducer installed on a
pipe through which a fluid flows, the method comprising using a
first piezoelectric element for a flow measurement and using the
second piezoelectric for obtaining a value for ultrasound velocity
in a fluid in the pipe.
[0023] Thus, a more accurate measurement of flow rate can be
obtained.
[0024] The method may comprise using the value of ultrasound
velocity to obtain a value of flow rate through the pipe.
[0025] According to a seventh aspect of the present invention is
provided a computer program comprising instructions for performing
the method.
[0026] According to a seventh aspect of the present invention is
provided a computer program product comprising a computer readable
medium (which may be non-transitory) storing the computer
program.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Certain embodiments of the present invention will now be
described, by way of example, with reference to the accompanying
drawings, in which:
[0028] FIG. 1 is a perspective view of a clamp-on ultrasonic
transducer assembly clamped onto a pipe, and which includes a
two-part clamp and two wedge-type ultrasonic transducers;
[0029] FIG. 2 is a perspective view of a first part of the clamp
shown in FIG. 1;
[0030] FIG. 3 is a perspective view of a second part of the clamp
shown in FIG. 1;
[0031] FIG. 4 is a perspective view of a wedge-type ultrasonic
transducer shown in FIG. 1;
[0032] FIG. 5 is a side view of the wedge-type ultrasonic
transducer;
[0033] FIG. 6 is a longitudinal cross-sectional view of the pipe
and a wedge-type ultrasonic transducer;
[0034] FIG. 7 is a perspective view of a wedge of PEEK;
[0035] FIG. 8 is a partial end elevation of a pipe and wedge;
and
[0036] FIG. 9 is a process flow diagram of a method of using the
wedge-type ultrasonic transducer.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0037] Referring to FIG. 1, a clamp-on ultrasonic transducer
assembly 1 is shown clamped around a pipe 2. The pipe 2 extends
along a longitudinal axis 3 and comprises a pipe wall 4 having an
outer surface 5. The clamp-on ultrasonic transducer assembly 1
(herein also referred to as a "clamp-on assembly", "clamp-on flow
meter" or simply "flow meter") comprises a generally cylindrical,
two-piece plastic pipe clamp 6 having first and second parts 7, 8
(or "halves").
[0038] Referring also to FIGS. 2 and 3, the first and second pipe
clamp parts 7, 8 comprise generally half-cylinder-shaped shells 9,
10 held together by a pair of hinges 11.sub.1, 11.sub.2 (mostly
obscured in FIG. 1) spaced apart along one side of the pipe clamp 6
and by a pair of closures 13.sub.1, 13.sub.2 (herein referred to as
"clips" or "clasps") spaced apart along the opposite side of the
pipe clamp 6.
[0039] The pipe clamp 6 holds first and second sensors 15,
15.sub.1,15.sub.2 in fixed positions in first and second slots
16.sub.1, 16.sub.2 respectively which are spaced apart along the
pipe 2. The slots 16.sub.1, 16.sub.2 have dimensions which match
those of the sensors 15.sub.1, 15.sub.2 such that the sensors
15.sub.1, 15.sub.2 fit securely in the slots 16.sub.1, 16.sub.2.
Thus, the slots 16.sub.1, 16.sub.2 can be used to locate the
sensors 9.sub.1, 9.sub.2 precisely with respect to each other. The
pipe clamp 6 presses the sensors 15.sub.1,15.sub.2 against the
outer surface 5 of the pipe wall 4. A single slot (not shown) or
slots 16.sub.1, 16.sub.2 which are longer than the sensors
15.sub.1, 15.sub.2 which can allow the separation of the sensors
15.sub.1, 15.sub.2 to be varied.
[0040] The same sensors 15,15.sub.1, 15.sub.2 can be used with
other, pipe clamps (not shown) having generally the same
configuration as the pipe clamp 6, but arranged to fit pipes of
other, different sizes (i.e. pipes having greater or smaller outer
diameter). Thus, identical sensors 9 can be produced, while
different sizes of the pipe clamps (not shown) can be formed,
thereby allowing clamp-on flow meters (not shown) for different
sizes of pipes to manufactured easily and/or cheaply.
[0041] Referring in particular to FIG. 2, the first pipe clamp part
7 comprises an elongate, generally half-cylinder-shaped shell 9 (or
"body") in which the first and second slots 16.sub.1, 16.sub.2 are
provided as rectangular through-holes. The first pipe clamp part 7
includes first and second first hinge parts 17.sub.1, 17.sub.2
(each first hinge part 17.sub.1, 17.sub.2 forming one half of a
hinge 11.sub.1, 11.sub.2) integrally formed with the shell 9. Each
first hinge part 17.sub.1, 17.sub.2 comprises an outwardly- and
downwardly-extending arm 18.sub.1, 18.sub.2 supporting a stub or
pin 19.sub.1, 19.sub.2. The first pipe clamp part 7 also includes
first and second first closure parts 20.sub.1, 20.sub.2 (each first
closure part 20.sub.1, 20.sub.2 forming one half of a respective
closure 131, 132) integrally formed with the body 9. The first
closure parts 20.sub.1, 20.sub.2 comprise a flap 21.sub.1, 21.sub.2
having an aperture 22.sub.1, 22.sub.2 having an inner wall
23.sub.1, 23.sub.2 providing a retaining surface.
[0042] Referring in particular to FIG. 3, the second pipe clamp
part 8 comprises an elongate, generally half-cylinder-shaped shell
10 (or "body"). The second pipe clamp part 8 includes first and
second second hinge parts 25.sub.1, 25.sub.2 (each second hinge
part 25.sub.1, 25.sub.2 forming one half of a hinge 11.sub.1,
11.sub.2) integrally formed with the shell 10. Each second hinge
part 25.sub.1, 25.sub.2 comprises an outwardly-extending arm
26.sub.1, 26.sub.2 supporting a respective half collar 27.sub.1,
27.sub.2 for receiving a respective pin 19.sub.1, 19.sub.2 form the
first pipe clamp part 7. The second pipe clamp part 8 includes
first and second second closure parts 28.sub.1, 28.sub.2 (each
second closure part 28.sub.1, 28.sub.2 forming one half of a clasp
13.sub.1, 13.sub.2) integrally formed with the body 10. The second
closure parts 28.sub.1, 28.sub.2 takes the form of a barbed head
comprising an inclined leading edge 29.sub.1, 29.sub.2 (or
"ramp-like tooth") and a perpendicular trailing edge 30.sub.1,
30.sub.2 for engaging with the retaining wall 23.sub.1,
23.sub.2.
[0043] Referring to FIGS. 4 to 6, the sensors 15 take the form of
ultrasonic transducers comprises an ultrasound-propagating element
36 (or "wedge") made from polyetheretherketone (PEEK). The wedge 36
is sufficiently narrow that it allows the wedge 36 to be formed by
injection moulding, in particular at lower pressures and
temperatures than normal. The wedge 36 does not include a filler,
such as glass fibre, to reinforce and/or to facilitate manufacture.
The wedge 36 is also sufficiently narrow that is can be used on a
variety of pipe diameter, for example, from 5 mm to 150 mm or
more.
[0044] The wedge 36 generally takes the form of a rectangular prism
having a chamfer. The wedge 36 comprises a first face 37 (herein
referred to as a "bottom face"), and second and third faces 38, 39
(herein referred to as a "first top face" and "second top face"
respectively) opposite the first face 37. The bottom face 37 is
preferably flat and is in direct contact with the outer surface 5
of the pipe wall 4.
[0045] The first top face 38 is inclined to the bottom face 37. The
second top face 39 lies parallel to the bottom face 37. The normal
40 of the bottom face 37 and the normal 41 of the first top face 38
subtend an angle 43.
[0046] The wedge 36 also includes fourth and fifth opposite faces
45, 46 (herein referred to as "first side" and "second side"
respectively). The bottom face 37 of the wedge 36 has a width, w,
which is equal to or less than 10 mm, preferably between 5 and 9 mm
and more preferably 6 mm. The bottom face 37 is preferably the
narrowest part of the wedge 36. The wedge 36 also includes sixth
and seventh opposite faces 47, 48 (herein referred to as "first
end" and "second end" respectively). The bottom face 37 of the
wedge 36 has a length, 1, between the first and second ends 47, 48.
The length, 1, is greater than the width, w, and is less than 80
mm. The wedge 36 has a height, h, between the bottom face 37 and
the second top face 39, which is between about 10 and 50 mm.
[0047] The sensor 15 includes a first piezoelectric element 49
which is mounted on the first top face 38 and which is directed
obliquely at the bottom face 37. The sensor 15 also includes a
second piezoelectric element 50 which is mounted on the second top
face 39 and is directed perpendicularly to the bottom face 37.
[0048] Referring also to FIG. 8, when the sensor 15 is in contact
with a pipe wall 4, the area of contact is a narrow rectangular
region having width less than the width, w. This is because the
bottom face 37 is flat and the pipe wall 4 is curved. The wedge 36
is narrower compared to conventional wedges. By making the wedge 36
narrower, not only are material costs reduced, but also the volume
of the wedge 36 is reduced to a size where it can be more easily
injection moulded.
[0049] The bottom face 37 of the wedge 36 may be moulded so that it
is cylindrically concave (i.e., transversely concave and
longitudinally straight) thereby helping to increase the area of
contact. Alternatively, the bottom face 37 of the wedge 36 may be
machined after moulding so that it is cylindrically concave. Even
if such a wedge 36 is machined after moulding, there can still be a
significant cost saving in the quantity of material used and the
amount of machining required, and potentially increase
manufacturing rate.
[0050] As hereinbefore described, the sensor 9 can be used on any
diameter of pipe 2 and can take the form of an insert in a pipe
clamp 6 (FIG. 1). The pipe clamp 6 (FIG. 1) can be configured for
use with any size of pipe 2. Thus, a faulty or damaged sensor 9 can
be easily replaced by slotting a replacement sensor 9 into an
appropriate slot 16.sub.1, 16.sub.2 (FIG. 1).
[0051] Referring in particular to FIGS. 4 to 7, the piezoelectric
elements 49, 50 adapted for a given frequency of operation can be
can easily be replaced with ones operating at a different
frequency. The sensor 15 may also be used in a sealed unit (not
shown). The ultrasonic sensor 1 has two piezoelectric elements 49,
50. However, only one in a pair of sensors 15 may use both
piezoelectric elements 49, 50, although each sensor 15 in the pair
may include two piezoelectric elements 49, 50 (with one element 49,
50 in one sensor 15 being redundant) for efficient
manufacturing.
[0052] Referring to FIGS. 4 and 5, a bracket 68 used for holding
electrical connectors 69, 70 (not shown in FIG. 4) and loading
screws 71, 72 can also be adapted to hold the piezoelectric
elements 49, 50 in position. The piezoelectric elements 49, 50 can
have a wrap-around electrode (not shown) or be provided with
electrodes (not shown) on both sides, if a shallow channel (not
shown) is machined into the wedge 36 to accept a soldered wire 73,
74 (not shown in FIG. 4).
[0053] In the illustrated embodiment, the piezoelectric elements
49, 50 are shown held in by a clamping arrangement using loading
plates 75, 76. However, the piezoelectric elements 49, 50 can be
glued into position using a layer of adhesive (not shown) between a
piezoelectric element 49, 50 and the wedge 36. The piezoelectric
elements 49, 50 can be coupled to the wedge 36 via a thin layer of
grease (not shown) or elastomeric material (no shown). Preferably,
a jig (not shown) is used to glue the elements 49, 50 to help
ensure accurate and reproducible placement.
[0054] Referring in particular to FIG. 6, when excited, the first
piezoelectric element 49 emits an ultrasonic wave 82 along a path
83. When excited, the second piezoelectric element 50 can send an
ultrasonic wave 84 along a path 85 into the pipe 2 and through the
liquid 86 so that, knowing the pipe material and dimensions, the
ultrasonic velocity in the liquid 86 can be measured and used in
the calculation of the flow velocity, or used to calculate the
temperature of the liquid 86.
[0055] Other measurements methods can be used. For example, if the
internal diameter of the pipe 2 is known, then a signal processor
(for example, in the form of a microcontroller or a computer) can
determine the speed of sound in the liquid 86 without further
information (e.g. without information about material properties).
Alternatively, if the outside diameter of the pipe 2 is known and
information about the pipe material are known, then the signal
processor can determine the speed of sound in the liquid 86.
[0056] Referring also to FIG. 9, a measurement system (not shown)
can perform a measurement of flow rate of the fluid 86 through the
pipe 2.
[0057] The measurement system (not shown) uses a first
piezoelectric element 49 of, for example, the first sensor 15.sub.1
(together with a first piezoelectric element 49 of the second
sensor 15.sub.2) to perform a flow measurement (step S1). The
measurement system (not shown) uses the second piezoelectric
element 50 of the first or second sensor 15.sub.1, 15.sub.2 to
obtain a value for ultrasound velocity in a fluid in the pipe (step
S2). The measurement system (not shown) uses the measured value of
ultrasonic wave velocity to calculate the flow rate (step S3).
[0058] First and second transverse through-holes 87, 88 pass
between the first and second sides 15, 16, proximate to the first
and second ends 47, 48. The through-holes 87, 88 can be used to
receive a rod or bar (not shown) for locating the wedge 36 in the
clamp 6 (FIG. 1) and for providing a point from which a spring (not
shown) can urge the wedge 36 against the pipe 2.
[0059] The first end 47 of the wedge 36 may patterned (not shown)
or have features (not shown) to provide a scattering surface to
discourage reverberation within the wedge 36 and simplify the
temporal profile of the received ultrasonic signal. For some types
of measurements, scattering features can be omitted as waves
reverberating within the wedge 6 may not be an issue. As mentioned
hereinbefore, the size and shape of the wedge 6 can simplify
manufacturing processes and reduce manufacturing costs, and more
readily lends itself to injection moulding and mass production.
MODIFICATIONS
[0060] It will be appreciated that various modifications may be
made to the embodiments hereinbefore described. Such modifications
may involve equivalent and other features which are already known
in the design, manufacture and use of clamp-on ultrasonic
transducers and component parts thereof and which may be used
instead of or in addition to features already described herein.
Features of one embodiment may be replaced or supplemented by
features of another embodiment.
[0061] Although claims have been formulated in this application to
particular combinations of features, it should be understood that
the scope of the disclosure of the present invention also includes
any novel features or any novel combination of features disclosed
herein either explicitly or implicitly or any generalization
thereof, whether or not it relates to the same invention as
presently claimed in any claim and whether or not it mitigates any
or all of the same technical problems as does the present
invention. The applicants hereby give notice that new claims may be
formulated to such features and/or combinations of such features
during the prosecution of the present application or of any further
application derived therefrom.
* * * * *